To date, proposals have been made on techniques for determining a degree of attention of a user to a content using a biosensor and a captured image. In the case of using a biosensor, methods of determining a degree of concentration of a user based on GSR (Galvanic Skin Response), Skin temperature, and BVP (Blood Volume Pulse) have been known. In the case of using an image, methods of calculating a degree of enthusiasm of a user by a posture of the user (leaning forward and leaning back) have been known.
As examples of related-art techniques, Japanese Laid-open Patent Publication Nos. 2003-111106 and 2006-41887 have been known.